1. Field of the Invention
The present invention relates to a bar code reader for reading a bar code by applying a laser beam emitted from a laser diode to the bar code, and receiving reflected light therefrom through a photodetector.
2. Description of the Related Art
A bar code reader for reading a bar code by the agency of reflected light of light applied from a light source towards the bar code is in widespread use today in the distribution sector, sales control division, and so forth because of its capability of reading the bar code even if the bar code reader is at a good distance away from the bar code.
Among such bar code readers, there is available one equipped with a portable laser scanning head which a user can hold in one hand. When reading a bar code printed on goods, and so forth, by use of the portable laser scanning head, a laser beam is caused to be emitted therefrom to be directed towards the bar code as a target of reading so as to reciprocatively scan the bar code in such a way as to cut across it, whereupon the laser beam reflected from the bar code is detected, and the bar code is read by decoding the detection signals (refer to, for example, JP, 5-233862, A, JP, 6-187481, A, and so forth).
Thus, with a bar code reader equipped with a laser diode, laser light emitted from the laser diode of the laser scanning head is rendered into a thin beam form. Such a laser beam is deflected by rotation of a rotary optical deflector such as a polygon mirror, galvanomirror, and so forth, thereby scanning a part (bar code surface) on which a bar code is printed.
However, because the laser light emitted by the laser diode is at a wavelength, close to that of an infrared ray, and in a boundary region between the visible region and the invisible region, it is difficult to visually recognize the laser beam in an environment of bright ambient light. In addition, because a scanning speed is very fast, there has arisen a problem that it is impossible to visually recognize a scanning position and a width of the laser beam on the bar code surface, and it is difficult to sight a scanning head on a bar code, rendering it difficult to read the bar code accurately and efficiently.
To overcome such a problem as described, there has been disclosed in, for example, JP, 5-233862, A, an optical scanning device equipped with an optical sighting mechanism for sighting a handy type laser scanning head on a bar code to be read by the same.
The optical sighting mechanism, however, requires a pair of light sources for sighting, an optical system associated therewith, and so forth, thereby rendering the constitution thereof complex, and increasing the number of components thereof, so that not only a high cost results, but also an application method thereof is far from simplicity.
Further, with a bar code reader disclosed in, for example, JP, 2000-90189, A, a proposal has been made to install a pair of mirrors for deflecting a laser beam scanning the vicinity of the opposite edges of a scanning range by the laser beam deflected by a scanning mirror which rotatively reciprocates, towards the center side of the scanning range. It is intended to thereby increase a quantity of light irradiated to a predetermined part in the vicinity of the center of the scanning range, so that visibility of a scanning line by the laser beam is enhanced.
With this method, however, there is a need of disposing the pair of the mirrors as added at a position closer to the bar code surface than the scanning mirror, thereby creating a problem in that the scanning head becomes larger. Furthermore, because the scanning line by the laser beam needs to be recognized in a state where scanning by the laser beam is executed by rotative reciprocation of the scanning mirror, it has still been difficult to visually recognize the scanning line if a scanning speed is fast.
The invention has been developed to solve such problems as described above, encountered by conventional bar code readers provided with a laser diode, and it is therefore an object of the invention to provide a bar code reader whose scanning position and a width of a laser beam on a bar code surface can be recognized without introduction of a complex mechanism and increasing the size of a scanning head even if a scanning speed of the laser beam is increased, so that anyone can easily implement focusing of the laser beam on a bar code of an optional length with the scanning head, enabling reading of the bar code to be executed accurately and efficiently.
Further, it is another object of the invention to enable either automatic scanning or manual scanning to be selected, and to enable reading of the bar code to be executed accurately and efficiently in either case.
To this end, there is provided a bar code reader provided with a laser diode and a rotatory optical deflector for deflecting a laser beam emitted by the laser diode for scanning, comprising a rotation position detection means for detecting a rotation position of the rotatory optical deflector at a position corresponding to a reading start edge of a laser beam scanning range of a bar code, a means for starting bar code reading by rotating the rotatory optical deflector again after stopping rotation of the rotatory optical deflector for only a predetermined time length upon the rotation position detection means detecting the rotation position of the rotatory optical deflector, and a means for stopping the rotation of the rotatory optical deflector for only a predetermined time length upon a laser beam scanning time length reaching a preset scanning time length up to the final position of the bar code reading after the bar code reading is started by the means for starting the bar code reading.
Or in place of the rotation position detection means described above, a rotation position detection means for detecting a rotation position of the rotatory optical deflector at a position before a reading start edge of a laser beam scanning range of a bar code may be provided, and bar code reading may be started by rotating the rotatory optical deflector again after stopping the rotation of the rotatory optical deflector for only a predetermined time length upon a laser beam scanning time length reaching a preset scanning time length up to a reading start position after the rotation position detection means detecting the rotation position of the rotatory optical deflector.
Further, with these features, a means for selecting either automatic scanning or manual scanning may be provided, and bar code reading may be started by rotating the rotatory optical deflector again after stopping the rotation of the rotatory optical deflector for only a predetermined time length upon the rotation position detection means detecting the rotation position of the rotatory optical deflector in the case of the automatic scanning being selected, subsequently stopping the rotation of the rotatory optical deflector for only a predetermined time length upon a laser beam scanning time length reaching a preset scanning time length up to the final position of the bar code reading, while the rotation of the rotatory optical deflector may be stopped through locking upon the laser beam scanning time length reaching a preset scanning time length up to the center position of the laser beam scanning range of the bar code after the rotation position detection means detecting the rotation position of the rotatory optical deflector in the case of the manual scanning being selected.
Otherwise, rotation of the rotatory optical deflector may be stopped for only a predetermined time length upon a laser beam scanning time length reaching a preset scanning time length up to a reading start position of the bar code reading after the rotation position detection means detecting the rotation position of the rotatory optical deflector in the case of the automatic scanning being selected, and subsequently, bar code reading may be started by rotating the rotatory optical deflector again, stopping the rotation of the rotatory optical deflector for only a predetermined time length upon the laser beam scanning time length reaching a preset scanning time length up to the final reading position of the bar code reading, while the rotation of the rotatory optical deflector may be stopped through locking upon the laser beam scanning time length reaching a preset scanning time length up to the center position of the laser beam scanning range of the bar code after the rotation position detection means detecting the rotation position of the rotatory optical deflector in the case of the manual scanning being selected.
Further, a first fixed optical deflector may be disposed in front of a collimator lens for rendering the laser light emitted by the laser diode into a laser beam of parallel light rays, in the outgoing direction of the laser beam, such that the laser beam deflected by the first fixed optical deflector is rotationally deflected by the rotatory optical deflector described above so as to scan the bar code, and a second fixed optical deflector may be provided so as to deflect the laser beam deflected by the first fixed optical deflector in a given direction when the rotatory optical deflector is situated in a rotation position outside the optical path of the laser beam described.
The second fixed optical deflector is preferably disposed on a side of the rotatory optical deflector, opposite from the first fixed optical deflector.
It is more preferable that the second fixed optical deflector is made up of a translucent reflector so as to reflect a portion of the laser beam falling on the second fixed optical deflector to be deflected into the given direction, allowing the rest of the laser beam to be transmitted therethrough, and a third fixed optical deflector is provided so as to deflect a transmitted portion of the laser beam into a direction differing from the given direction.
In such a case, the second fixed optical deflector is preferably disposed on a side of the rotatory optical deflector, opposite from the first fixed optical deflector, and the third fixed optical deflector is disposed further behind the second fixed optical deflector.
Further, the invention is preferably provided with the rotation position detection means for detecting the rotation position of the rotatory optical deflector, and temporary rotation stoppage means for stopping rotation of the rotatory optical deflector for only a predetermined time length when it is decided on the basis of the detection result of the rotation position detection means that the rotatory optical deflector is situated in the rotation position outside the optical path of the laser beam deflected by the first fixed optical deflector.
In other respect, with a bar code reader provided with a means for selecting either automatic scanning or manual scanning, there may be provided a rotation position detection means for detecting a rotation position of the rotatory optical deflector at two spots corresponding to the opposite edges of the laser beam scanning range of the bar code, respectively, and at a spot situated between the two spots, and means for stopping rotation of the rotatory optical deflector for only a predetermined time length upon the rotation position detection means detecting the rotation position of the rotatory optical deflector at the two spots, respectively, in the case of the automatic scanning being selected, and for stopping the rotation of the rotatory optical deflector through locking upon the rotation position detection means detecting the rotation position of the rotatory optical deflector at the spot situated between the two spots in the case of the manual scanning being selected.
With these features, there may be provided a means for slowing down a rotation speed of the rotatory optical deflector during a period of bar code reading from a time of the rotation position detection means detecting one of the rotation positions at the two spots up to the rotation position detection means detecting the other of the rotation positions, while rotating the rotatory optical deflector at a higher speed at other times in the case of the automatic scanning being selected, and for stopping the rotation of the rotatory optical deflector through locking upon the rotation position detection means detecting the rotation position of the rotatory optical deflector at the spot situated between the two spots in the case of the manual scanning being selected.
Otherwise, there may be provided a means for detecting rotation positions of the rotatory optical deflector at two spots corresponding to the opposite edges of the laser beam scanning range of the bar code, respectively, and means for stopping rotation of the rotatory optical deflector for only a predetermined time length upon the means detecting the rotation positions of the rotatory optical deflector at the two spots, respectively.
Or it is preferable to provide means for reducing a rotation speed of the rotatory optical deflector during a time period from a time of the rotation position detection means described above detecting a rotation position of the rotatory optical deflector corresponding to the scanning start edge, up to a time of the rotation position detection means detecting a rotation position of the rotatory optical deflector corresponding to a scanning completion edge, from a rotation speed at other times.
The above and other objects, features and advantages of the invention will be apparent from the following detailed description which is to be read in conjunction with the accompanying drawings.